Master Lock No 975

= Master Lock No 975 =

Master Lock No 975 is a resettable combination padlock made by Master Lock. It has four dials with the digits 0-9. This results in total of 10,000 theoretical permutations.

The Master Lock No 975 series includes solid brass bodied locks. Master now makes the same lock in steel as a model of M175 and M1175.

Operating Instructions

 * 1) Move each of the four dials to the correct digit
 * 2) Pull on the shackle
 * 3) If the combination is correct the shackle will be free

Internals
The lock has a detainer in the center with fingers that fit in to gates on the wheels. The detainer blocks the pawls from moving in until all the gates in the wheels are facing up to allow the detainer to move down. That allows the pawls to move in.

Vulnerabilities
The Master Lock No 975 series may be vulnerable to one or more of the following:


 * Decoding - This lock can be decoded by pulling the shackle out and holding it there. Then move the first dial back and forth to see how much give it has in both directions.  The true gate/correct number will have more play than the others.  Release the shackle, increment the dial by one, and re-tension the shackle.  Check the play in the dial again.  After you find the number with the most play back and forth, go through the same for each dial.

Gallery
Add to me!